Cement additive, and concrete composition and structure both containing the same

ABSTRACT

A cement additive composition for preventing discoloration of the surface of concrete, comprising a cement additive (a) and a water-reducing admixture (b), the additive (a) comprising a mixture of compounds represented by the general formula (1): 
     
       
         R 1 O(AO)n 1 H  ( 1 ) 
       
     
     (wherein R 1  is a C 1-6  alkyl group, A is an ethylene group and/or a propylene group, and n 1  is a number of 1 or more), containing all the compounds satisfying n 1 =2 to 6 in a total amount of not less than 40% by mass, and having an average n 1  of 1.5 to 10, a molecular weight distribution Mw/Mn of not less than 1.05, a Z average molecular weight Mz of not less than 200 and a ratio of (a):(b) by mass of (5 to 99.5):(95 to 0.5). It can prevent the discoloration of the surface of concrete.

TECHNICAL FIELD

The present invention relates to a cement additive.

BACKGROUND ART

Generally, the surface of cement, mortar and concrete exposed to the airhas the problem of gradual discoloration with time by the action ofsunray, dust in the air, microorganisms etc. Accordingly, a method ofreducing a water-cement ratio or using a water-permeable concrete form,or applying a water repellant onto the surface of concrete has beenknown as the method of suppressing discoloration.

One serious drawback of cement, mortar and concrete is that there easilyoccurs cracking on drying, which is attributable to high shrinkage ofcement on drying. Accordingly, various reducing agents for reducing theshrinkage of cement compositions on drying have been proposed, and forexample an adduct of alcohol with alkylene oxide (hereinafterabbreviated to AO) and an adduct of alkyl phenol with AO are known(e.g., U.S. Pat. No. 4,547,223 and JP-B 62-10947).

The conventional methods known to suppress discoloration of the surfaceof concrete are problematic in that special attention should be paid tothe compounding method, the type of concrete form, and application ofthe water repellant.

Further, the conventional admixtures for reducing the shrinkage ofcement, when added to concrete compositions, have the problem that theair content is easily influenced by the mixed concrete temperature, andif the air content is attempted to be regulated by an air-entrainingadmixture, a slight difference in the amount of the air-entrainingadmixture leads to a change in the air content in concrete, thus causingthe problem that concrete containing a predetermined air content ishardly obtained.

DISCLOSURE OF INVENTION

The present inventors extensively studied a cement additive forpreventing discoloration of the surface of concrete and a cementadditive for easily regulating the air content in concrete, and as aresult they arrived at the present invention.

That is, the present invention relates to [I] a cement additivecomposition for preventing discoloration of the surface of concrete,which comprises a cement additive (a) and a water-reducing admixture(b), wherein (a) comprises a mixture of compounds represented by thegeneral formula (1):

R₁O(AO)n₁H  (1)

(wherein R₁ is a C₁₋₆ alkyl group, A is an ethylene group and/or apropylene group, and n₁ is a number of 1 or more), and all the compoundswherein n₁ is 2 to 6 are present in (a), the total content thereof (i.e.the content of the compounds wherein n₁=2 to 6) is 40% by mass or more,the average of n₁ is 1.5 to 10, the molecular weight distribution Mw/Mnis 1.05 or more, the Z average molecular weight Mz is 200 or more, andthe ratio of (a):(b) by mass is (5 to 99.5):(95 to 0.5).

Further, the present invention relates to [II] a cement additivecomposition, which comprises a combination of (c) a compound or amixture of two or more compounds represented by the general formula (2):

R₂O(AO)n₂H  (2)

(wherein R₂ is hydrogen or a C₁₋₆ alkyl group, A is an ethylene groupand/or a propylene group, and n₂ is a number of 1 to 10 on average) and(d) a compound or a mixture of two or more compounds represented by thegeneral formula (3):

R₃O(C₃H₆O)n₃H  (3)

(wherein R₃ is a C₁₋₄ alkyl group, and n₃ is a number on average of atleast n₂ +1 or of more than 10 to 100), the ratio of (c):(d) by massbeing 100:(0.01 to 1).

Further, the present invention relates to [III] a concrete compositioncomprising a cement, any one of the above compositions in an amount of0.5 to 10% based on the mass of the cement, water and an aggregate.

Further, the present invention relates to [IV] a concrete structureproduced by hardening the concrete composition described above.

DETAILED DESCRIPTION OF THE INVENTION

In the general formulae (1) and (2), the alkyl group R₁ and R₂ include aC₁₋₆ straight-chain or branched alkyl group such as methyl, ethyl, n-and i-propyl, n-, i- and t-butyl, n-, i- and t-pentyl, and n- andi-hexyl. The alkyl group is preferably a C₁₋₄ alkyl group, morepreferably methyl and a straight-chain or branched butyl group.

In the general formula (1) and (2), A is an ethylene group and/or apropylene group, and AO is an oxyethylene group and/or an oxypropylenegroup, which are formed usually by adding ethylene oxide (hereinafterabbreviated to EO) and/or propylene oxide (hereinafter abbreviated toPO). If EO and PO are added in combination, they may be added in anarbitrary ratio (e.g., a molar ratio of from 1:99 to 99:1) in either ablock or random form. When EO and PO are added in combination, blockaddition is preferable.

The additive (a) comprises a mixture of compounds represented by thegeneral formula (1), in which the total content of the compounds whereinn₁ is 2 to 6 is 40% or more, preferably 50% or more. In the generalformula (1), n₁ is a number of 1 or more, preferably a number of 1 to10. The average of n₁ is 1.5 to 10, preferably 2 to 7. In the foregoingand following description, % refers to % by mass unless otherwisespecified.

The molecular weight distribution (Mw/Mn) of (a) [Mw and Mn referrespectively to weight-average and number-average molecular weightsdetermined by gel permeation chromatography (GPC)] is 1.05 or more,preferably from 1.07 to 2. The Mz of (a) (determined by GPC) is 200 ormore, preferably 250 to 1000. If (a) is outside of this range, it is notpossible to achieve an excellent effect of preventing discoloration ofthe surface of concrete.

Insofar as the water-reducing admixture (b) used in the presentinvention is an admixture used generally for concrete, its compositionis no limited. The water-reducing admixture (b) includes e.g. materialsordinarily used as air-entraining and water-reducing admixtures,high-range water-reducing admixtures, air-entraining and high-rangewater-reducing admixtures and superplasticizer [described in e.g.“Developed Techniques of Concrete Admixtures” published by C. M. C. Ltd.(1995)], and examples of such materials include lignin sulfonates (i.e.salts of alkali metals such as sodium and salts of alkaline earth metalssuch as calcium; this also applies to salts of the following compounds),naphthalin sulfonate formalin condensate salts (degree of condensation:5 to 20), melamine sulfonate formalin condensate salts (degree ofcondensation: 5 to 20), polycarbonates [e.g. poly(meth)acrylate having aMn of 5000 to 60,000, wherein (meth)acrylate means-acrylate and/ormethacrylate, and this also applies throughout the description of thespecification], aminosulfonate formalin condensate salts (degree ofcondensation: 2 to 20), and polycarboxylates [e.g. (meth)acrylicacid-(meth)acrylic acid polyoxyalkylene ester copolymer having a Mn of10,000 to 600,000] containing polyether group (e.g. polyoxyalkylenegroup having a polymerization degree of 10 to 200, containing 2 and/or 3carbon atoms in the alkylene group thereof), and these may also be usedin combination. Preferable among these water-reducing admixtures arelignin sulfonates, naphthalin sulfonate formalin condensate salts,polycarboxylates and polyether group-containing polycarboxylates, morepreferably lignin sulfonates and polyether group-containingpolycarboxylates.

In the cement additive composition of the present invention [I], theratio by mass of additive (a):water-reducing admixture (b) is (5 to99.5):(95 to 0.5), preferably (20 to 99):(80 to 1). Here, the mass of(b) refers to the net weight of the water-reducing admixture asnonvolatile matter, that is, the mass from which a diluent such as waterwas removed. If (a) is less than 5%, the effect of preventingdiscoloration of the surface of concrete is not satisfactory, while ifit exceeds 99.5%, the predetermined workability (particularlyconsistency) as concrete cannot be achieved.

Before preparation of the concrete composition, (a) and (b) may bepreviously mixed, or during preparation of the concrete composition, (a)and (b) may be separately added and mixed in the concrete composition.

In the general formula (2), n₂ is a number of 1 to 10 on average.Preferably, it is a number of 1.5 to 10 on average, more preferably anumber of 2 to 7 on average.

(c) is preferably the compound where R₂ is an alkyl group, and (c) isparticularly preferably the above-described (a). When (c) is theabove-described (a), an excellent shrinkage-reducing effect isdemonstrated.

In the general formula (3), R₃ is a C₁₋₄, straight-chain or branchedalkyl group. Such group includes those exemplified for R₁. The group ispreferably a straight-chain or branched butyl group.

C₃H₆O is formed usually by addition of PO.

n₃ is a number on average of at least n₂+1 or of more than 10 to 100. n₃is preferably a number of 10 to 100 on average, more preferably a numberof 10.1 to 95 on average, particularly preferably a number of 12 to 90on average and most preferably a number of 20 to 80 on average. When n₃is 10 or less and simultaneously less than n₂+1, the air content isincreased upon addition of the composition to concrete, while if n₃exceeds 100, defoaming properties are increased so that concrete withthe predetermined air content cannot be obtained.

In the cement additive composition of the present invention [II], theratio by mass of (c):(d) is 100:(0.01 to 1), preferably 100:(0.05 to0.8). When (d) is less than 0.01 or greater than 1, concrete having thepredetermined air content is hardly obtainable, and the resultingcomposition is not sufficiently satisfactory for practical use.

The composition of the present invention [II] comprises two or morecomponents comprising (c) and (d), and therefore two or more peakmolecular weights are present in its molecular weight distributioncurve. In the method of mixing (c) with (d), they may be previouslymixed, or during preparation of the concrete composition, (c) and (d)may be separately added and mixed in the concrete composition.

In the cement additive composition of the present invention [II], awater-reducing admixture is preferably used in combination to furtherimprove the shrinkage-reducing effect. The water-reducing admixtureincludes those described for the water-reducing admixture (b), andpreferable examples thereof are also described therein.

The ratio by mass of the total of (c) and (d):(b) is preferably (5 to99.5):(95 to 0.5), more preferably (20 to 99):(80 to 1). When the totalof (c) and (d) is in the range of 5 to 99.5%, a sufficientshrinkage-preventing effect is demonstrated, and there is no problemwith workability (particularly consistency) as concrete.

Cement to which the additive composition of the present invention isadded is conventional hydraulic cement. That is, mention is made ofvarious kinds of Portland cement such as normal Portland cement(high-early-strength Portland cement, moderate-heat Portland cementetc.), blended cement (Portland blast-furnace slag cement, Portlandfly-ash cement etc.).

The amount of the cement additive composition of the present invention[I] or [II] added to the concrete composition of the present invention[III] is varied depending on the number of carbon atoms in the alkylgroup of the compound represented by the general formula (1) or (2), butits amount is usually 0.5 to 10%, preferably 1 to 8% relative to thecement. If the amount of the cement additive composition used is lessthan 0.5%, the resulting concrete composition is poor in the effect ofpreventing discoloration of the surface of concrete or in the effect ofreducing shrinkage, while if it exceeds 10%, the resulting concretecomposition is practically not satisfactory because the strength ofconcrete is about ⅔ or less relative to the strength of concrete towhich the composition was not added. Further, the amount of thewater-reducing admixture (b) in the present invention [II] is preferably5% or less, more preferably 0.05 to 4% relative to the cement. If itsamount is 5% or less, the influence thereof on the strength of concreteis low.

The means of adding the additive composition may be the same as forconventional concrete admixtures. For example, a suitable amount of theadditive composition may be admixed with water to be admixed, or may beadded to once mixed fresh concrete. Alternatively, the additivecomposition may be allowed to penetrate into the surface layer of acement product.

The additive composition of the present invention is not limited by theadmixture used. That is, the additive composition can be used incombination with conventional air-entraining admixture (AE admixture)used in concrete, such as resinates and surfactants (polyoxyethylenealkyl aryl ethers etc.); known expansive additives based on calciumsulfoaluminate or quicklime; known accelerators such as calciumchloride, triethanolamine etc.; known retarders such as polyhydricalcohols, sugars, oxycarboxylates etc.; known corrosion inhibitors suchas nitrites etc.; and other known admixtures for mortar or concrete.These admixtures are described in “Developed Techniques of ConcreteAdmixtures” supra.

In the composition of the present invention [III], the amount of theadmixture used is varied depending on the type of the admixture but maybe in the ordinarily used range. For example, the amount of theair-entraining admixture (AE admixture) is usually 0.1% or less,preferably 0.001 to 0.06% relative to the cement.

The cement additive composition of the present invention can be used incombination with a shrinkage-reducing admixture [described in e.g.“Developed Techniques of Concrete Admixtures” supra] such as phenol oralkyl (C₁₋₃) phenol AO (EO and/or PO) adduct (number of moles of AOadded: 1 to 10) and polypropylene glycol (number average molecularweight: 500 to 1500) as a component other than those in the cementadditive composition of the present invention.

The amount of the shrinkage-reducing admixture other than the componentsin the cement additive composition of the present invention [I] or [II]is preferably 50% or less based on the additive composition of thepresent invention. In the case of 50% or less, the effect of preventingdeterioration of the surface of concrete or the easiness of regulatingthe air content in concrete is not deteriorated.

The total amount of the cement additive other than the cement additivecomposition of the present invention and the water-reducing admixture(b) in the present invention is preferably 5% or less, more preferably0.01 to 4% relative to the cement.

Water used in the concrete composition of the present invention [III] iswater prescribed in Document 9 attached to Japanese Industrial Standard(JIS) A 5308, and such water includes tap water, other water (water inrivers, lakes and marshes, well-water, etc.), recovered water etc.

In the composition of the present invention, water is used preferably insuch an amount that the water/cement ratio (i.e. % of water relative tocement) becomes 65 to 20%. In the case of 65% or less, sufficientconcrete strength can be achieved, and in the case of 20% or more, goodworkability (particularly consistency) can be achieved by use of thewater-reducing admixture.

In the concrete composition of the present invention [III], theaggregate includes fine aggregate and coarse aggregate. The fineaggregate used includes the aggregate prescribed in Document 1 attachedto JIS A 5308. Such aggregate includes river sand, land sand, pit sand,sea sand, crushed sand etc.

The fine aggregate is compounded in an amount of 500 to 1200 kg per m³of concrete. By compounding this amount of fine aggregate, the productis excellent in both concrete strength and workability (particularlyconsistency).

The coarse aggregate used in the concrete composition of the presentinvention [III] includes the aggregate prescribed in Document 1 attachedto JIS A 5308. Such aggregate includes river gravel, land gravel, pitgravel, crushed stone etc.

The coarse aggregate is compounded preferably in an amount of 500 to1200 kg per m³ of concrete. By compounding this amount of coarseaggregate, the product is excellent in both concrete strength andworkability (particularly consistency).

In the composition of the present invention [III], the proportion offine aggregate (sand-total aggregate ratio) is preferably 35 to 70% byvolume. The proportion of fine aggregate indicates the volume % of fineaggregate relative to the total amount of fine aggregate and coarseaggregate, and the optimum proportion of fine aggregate is varieddepending on the type and shape of aggregate used, and usually theproportion of fine aggregate is determined in a test such that the unitamount of water becomes minimized within a range in which predeterminedworkability (particularly consistency) is achieved.

The concrete structure of the present invention [IV] is obtained byhardening the concrete composition of the present invention [III], andthe method of hardening thereof is not particularly limited and may be aconventional method. The hardening or curing method may be air dryingcuring, humid air curing, underwater curing, accelerated curing byheating (steam curing, autoclave curing) and these can also be used incombination.

In the concrete structure of the present invention [IV] wherein thecement additive composition of the present invention [I] was added tocement in an amount of 2.25%, the reduction in lightness of the surfaceof the concrete structure after 5 years is usually in the range of 2 to4, as compared with a usual reduction of 9 or more in concrete to whichthe composition was not added, thus indicating a superior effect ofpreventing discoloration of the surface of the concrete structure.

Further, in the case of the concrete structure wherein the cementadditive composition of the present invention [II] was added to cementin an amount of 2.25% while the air-entraining admixture (AE admixture)was added to cement in a varying amount from 0.002% to 0.01%, an aircontent therein is usually in the range of 2 to 7% by volume, ascompared with an air content is sometimes either less than 2% or higherthan 8% by volume upon addition of the conventional shrinkage-reducingagent, thus indicating less influence of the varying amount of the AEadmixture on air entrainment thereby achieving easy regulation of theair content in concrete.

Best Mode for Carrying out the Invention

Hereinafter, the present invention is described in more detail byreference to the Examples, which are not intended to limit the presentinvention. In the Examples, the term “parts” refers to “parts by mass”.

In a test method on the effect of preventing discoloration, a testspecimen having a thickness of 15 cm, a height of 100 cm and a width of50 cm assumed to be used as a wall member was prepared for eachcompounding condition. 7 days after, the test specimen was removed froma concrete form and subjected to air-curing at room temperature for 28days. Thereafter, the test specimen was installed outdoors in Tokyo withits poured surface up and its 50 cm×100 cm surface toward north andsouth. As the concrete form, a urethane-coated plywood was used.

The color of the surface of each test specimen was measured by an L*a*b*color-specifying meter (JIS Z 8729) using a contact-type colorimetriccolor difference meter (Minolta Co., Ltd.), and the effect of preventingdiscoloration was evaluated in terms of lightness (L value). As regardsthe measurement position, color measurement was conducted at 10 sites intotal apart by 5 cm, 15 cm, 25 cm, 35 cm and 45 cm from the left-handside on the horizontal line apart by 15 cm and 30 cm from the upper endof the north surface. The results are expressed in terms of the averageof L values at the 10 sites. The measurement was conducted at the startof the exposure test and after 5 years of exposure, respectively.

Further, the slump was measured according to JIS A 1101, the air contentin concrete was measured according to JIS A 1128 and the degree ofshrinkage was measured according to JIS A 1129. A φ10×20 cm concretesample was prepared according to JIS A 1132 and subjected to underwatercuring at 20° C. for 28 days and measured compressive strength accordingto JIS A 1108.

The raw materials of concrete used in the Examples and ComparativeExamples are as follows.

In the following, Me is methyl alcohol, n-Bu is n-butyl alcohol, i-Bu isi-butyl alcohol, and the value in the parenthesis indicates the averagenumber of moles of units added; for example Me-EO (1)-PO (4) indicates amethyl alcohol-ethylene oxide (average number of moles of EO added:1)-propylene oxide (average number of moles of PO added: 4) blockadduct.

Cement Additive (a) in the Present Invention [I]

TABLE 1 Cement Additives (a) in the present invention [I] and theircomparative additives (R) Compound represented by general formula (1)Average Symbol Type (%) *1 of n₁ Mw/Mn Mz a-1 Me-EO(1)-PO(4) 91 5 1.09377 a-2 n-Bu-PO(2)-EO(2) 71 4 1.13 435 R-1 n-Bu-EO(2) 100 2 1.00 170 R-2n-Bu-PO(8)-EO(8) 9 16 1.18 1463 *1 Total mass % of compounds of generalformula (1) where n₁ is 2 to 6.

The Mw, Mn and Mz in Table 1 were measured under the followingconditions:

Measuring unit:

GPC system [HLC-8120GPC] manufactured by Tosoh.

Eluent:

Type, tetrahydrofuran

Flow rate, 0.6 (ml/min.)

Columns:

TSK gel Super H2000

+TSK gel Super H3000

+TSK gel Super H4000

Cement Additive Compositions (C) of the Present Invention [II]

C-1: A composition of 100 parts of Me-PO (3) and 0.05 part of n-Bu-PO(30)

C-2: A composition of 100 parts of n-Bu-EO (2) and 0.1 part of n-Bu-PO(30)

C-3: A composition of 100 parts of n-Bu-PO (2)-EO (2) and 0.5 part ofi-Bu-PO (50)

C-4: A composition of 100 parts of Me-EO (1)-PO (4) and 0.05 part ofn-Bu-PO (30)

Comparative Cement Additives or Cement Additive Compositions (R)

R-3: Me-PO (3)

R-4: n-Bu-PO (2)-EO (2)

R-5: A composition of 100 parts of n-Bu-PO (2)-EO (2) and 3 parts ofn-Bu-PO (30)

R-6: A composition of 100 parts of n-Bu-PO (2)-EO (2) and 0.1 part ofn-Bu-PO (120)

R-7: Me-EO (1)-PO (4)

Water-Reducing Admixtures (b)

b-1: Air-entraining and water-reducing admixture (Pozzolith No. 70,produced by NMB)

b-2: Air-entraining and high-range water-reducing admixture (RheobuildSP-8S, produced by NMB)

The above “Pozzolith” and “Rheobuild” are registered trademarks.“Microair” in the AE admixture (H) below is also a registered trademark.

Cement (D)

D-1: Normal Portland cement (produced by Taiheiyo Cement Corp.)

Water (E)

E-1: Tap water

Fine Aggregate (F)

F-1: Crushed sand (specific gravity: 2.60, fineness modulus=2.80,produced by Chichibu Kogyo Co., Ltd.)

Coarse Aggregate (G)

G-1: Crushed stone (2005, specific gravity of 2.60, produced by ChichibuKogyo Co., Ltd.)

AE Admixture (H)

H-1: Microair 303A produced by NMB

EXAMPLES 1 TO 4 Comparative Examples 1 to 5

Concrete structures (wall members) were constructed by hardeningconcrete compositions with the mix propotion shown in Table 2. Theresults of the consistency (slump) of the resulting concretecompositions and the color difference of the surface of concrete afteroutdoor exposure for 5 years are shown in Table 3 In Comparative Example5, a composition with objective slump could not be obtained and couldnot be poured, and thus color difference could not be measured.

The products of the present invention indicated a reduction of 2 to 3 inlightness after 5 years, and their discoloration could be sensed atslight degrees. On the other hand, the comparative products indicated areduction of about 10 to 12 in lightness after 5 years, and the darkdiscoloration of the surface could be clearly sensed. From theforegoing, it is understood that the surface of the concrete structuresobtained by hardening the cement additive composition of the presentinvention [I] for preventing discoloration of the surface of concreteundergoes less discoloration.

TABLE 2 Mix propotion of Concrete Cement Water-reducing additiveadmixture Sand- Quantity of material per unit volume of AdditionAddition Water- total concrete (kg/ ) amount amount Objective cementaggregate Fine Coarse (%/ (%/ slump ratio ratio Water ¹⁾ Cementaggregate aggregate Type cement) Type cement) (cm) (%) (%) E-1 D-1 F-1G-1 Product 1 a-1 2.0 b-1 0.25 18 ± 2 55 45 165 300 826 1012 of the 2a-1 2.0 b-2 0.80  8 ± 2 40 42 151 378 758 1051 Invention 3 a-2 2.0 b-10.25 18 ± 2 55 45 165 300 826 1012 4 a-2 2.0 b-2 0.80  8 ± 2 40 42 151378 758 1051 Compara- 1 — — b-1 0.25 18 ± 2 55 45 165 300 826 1012 tive2 R-1 2.0 b-1 0.25 18 ± 2 55 45 165 300 826 1012 Example 3 R-2 2.0 b-10.25 18 ± 2 55 45 165 300 826 1012 4 a-1 0.01 b-1 0.25 18 ± 2 55 45 165300 826 1012 5 a-2 2.0 b-1 0.005 18 ± 2 55 45 165 300 826 1012 ¹⁾Because the cement additive is added as a part of water, the amount ofwater + cement additive is shown

TABLE 3 Test results of concrete Lightness At the start of the Afterexposure Slump (cm) exposure test for 5 years Product of the 1 18.5 59.456.1 Invention 2 8.5 57.1 54.3 3 17.5 60.0 57.2 4 8.0 56.6 54.0Comparative 1 18.0 59.1 49.5 Product 2 17.5 59.6 47.8 3 17.0 58.9 46.7 418.5 59.3 47.4 5 2.5 — —

EXAMPLES 5 to 16 Comparative Examples 6 to 20

When the concretes shown in Tables 4-1 and 4-2 were mixed attemperatures of 10° C., 20° C. and 30° C., the amounts of AE admixturefor achieving the desired air content (4.5±1.5% by volume) are shown inTables 5-1 and 5-2. Further, the measurement results of the degree ofshrinkage and compressive strength of these concretes are shown inTables 5-1 and 5-2.

As can be seen from the results in Tables 5-1 and 5-2, the influence ofthe mixed concrete temperature on air entrainment is low when the cementadditive composition of the present invention [II] is used. Further, thedegree of shrinkage and compressive strength are not problematic ascompared with the case where the conventional shrinkage-reducing agentis used.

TABLE 4-1 Mix propotion of Concrete Water reducing Sand Quantity ofmaterial per unit Cement additive admixture Objective Water- totalvolume of concrete (kg/ ) Addition Addition air cement aggregate FineCoarse amount amount Slump content ratio ratio Water ¹⁾ Cement aggregateaggregate Type (%/cement) Type (%/cement) (cm) (%) (%) (%) E-1 D-1 F-1G-1 Product 5 C-1 2.0 b-1 0.25 18 ± 2 4.5 ± 55 45 165 300 826 1012 ofthe 6 C-1 4.0 b-1 0.25 18 ± 2 1.5 55 45 165 300 826 1012 Invention 7 C-12.0 b-2 0.80  8 ± 2 40 42 151 378 758 1051 8 C-2 2.0 b-1 0.25 18 ± 2 5545 165 300 826 1012 9 C-2 4.0 b-1 0.25 18 ± 2 55 45 165 300 826 1012 10C-2 2.0 b-2 0.80  8 ± 2 40 42 151 378 758 1051 11 C-3 2.0 b-1 0.25 18 ±2 55 45 165 300 826 1012 12 C-3 4.0 b-1 0.25 18 ± 2 55 45 165 300 8261012 13 C-3 2.0 b-2 0.80  8 ± 2 40 42 151 378 758 1051 14 C-4 2.0 b-10.25 18 ± 2 55 45 165 300 826 1012 15 C-4 4.0 b-1 0.25 18 ± 2 55 45 165300 826 1012 16 C-4 2.0 b-2 0.80 18 ± 2 40 42 151 378 758 1051 ¹⁾Because the cement additive is added as a part of water, the amount ofwater + cement additive is shown.

TABLE 4-2 Mix propotion of Concrete Quantity of material per unit Waterreducing Sand volume of concrete (kg/ ) Cement additive admixtureObjective Water- total Fine Coarse Addition Addition air cementaggregate aggre- aggre- amount amount Slump content ratio ratio Water ¹⁾Cement gate gate Type (%/cement) Type (%/cement) (cm) (%) (%) (%) E-1D-1 F-1 G-1 Compara- 6 R-3 2.0 b-1 0.25 18 ± 2 4.5 ± 1.5 55 45 165 300826 1012 tive 7 R-3 4.0 b-1 0.25 18 ± 2 55 45 165 300 826 1012 Example 8R-3 2.0 b-2 0.80  8 ± 2 40 42 151 378 758 1051 9 R-4 2.0 b-1 0.25 18 ± 255 45 165 300 826 1012 10 R-4 4.0 b-1 0.25 18 ± 2 55 45 165 300 826 101211 R-4 2.0 b-2 0.80  8 ± 2 40 42 151 378 758 1051 12 R-5 2.0 b-1 0.25 18± 2 55 45 165 300 826 1012 13 R-5 4.0 b-1 0.25 18 ± 2 55 45 165 300 8261012 14 R-5 2.0 b-2 0.80  8 ± 2 40 42 151 378 758 1051 15 R-6 2.0 b-10.25 18 ± 2 55 45 165 300 826 1012 16 R-6 4.0 b-1 0.25 18 ± 2 55 45 165300 826 1012 17 R-6 2.0 b-2 0.80  8 ± 2 40 42 151 378 758 1051 18 R-72.0 b-1 0.25 18 ± 2 55 45 165 300 826 1012 19 R-7 4.0 b-1 0.25 18 ± 2 5545 165 300 826 1012 20 R-7 2.0 b-2 0.80 18 ± 2 40 42 151 378 758 1051 ¹⁾Because the cement additive is added as a part of water, the amount ofwater + cement additive is shown.

TABLE 5-1 Test Results of Concrete Mixed Concrete Temperature 10° C. 20°C. 30° C. Amount of Degree of Compressive Amount of Degree ofCompressive Amount of Degree of Compressive AE shrinkage strength AEshrinkage strength AE shrinkage strength admixture (91 days) (28 days)admixture (91 days) (28 days) admixture (91 days) (28 days) (%/cement)(×10⁻⁴) (N/ ) (%/cement) (×10⁻⁴) (N/ ) (%/cement) (×10⁻⁴) (N/ ) Product5 0.003 3.52 36.5 0.005 3.71 35.8 0.006 3.81 35.0 of the 6 0.005 2.1735.2 0.007 2.20 34.3 0.009 2.37 33.7 Invention 7 0.008 3.40 48.3 0.0103.52 46.7 0.013 3.63 46.6 8 0.004 3.67 35.7 0.005 3.67 34.9 0.007 3.7833.3 9 0.004 2.24 34.1 0.006 2.19 33.4 0.008 2.52 33.1 10 0.009 3.5349.0 0.011 3.45 47.7 0.013 3.74 48.5 11 0.005 3.46 35.8 0.006 3.49 35.10.008 3.55 35.2 12 0.005 2.35 34.4 0.006 2.51 33.0 0.009 2.66 32.0 130.009 3.31 47.5 0.012 3.46 47.6 0.015 3.63 45.4 14 0.003 3.49 35.1 0.0053.53 34.8 0.006 3.55 34.0 15 0.005 2.25 34.0 0.006 2.30 33.5 0.008 2.3433.1 16 0.008 3.23 48.3 0.011 3.25 46.9 0.013 3.32 46.8

TABLE 5-2 Test Results of Concrete Mixed Concrete Temperature 10° C. 20°C. 30° C. Amount of Degree of Compressive Amount of Degree ofCompressive Amount of Degree of Compressive AE shrinkage strength AEshrinkage strength AE shrinkage strength admixture (91 days) (28 days)admixture (91 days) (28 days) admixture (91 days) (28 days) (%/cement)(×10⁻⁴) (N/ ) (%/cement) (×10⁻⁴) (N/ ) (%/cement) (×10⁻⁴) (N/ ) Compara-6 *1 — —  0.002 3.71 35.5  0.029 3.81 35.0 tive 7 *1 — —  0.001 2.2534.0  0.033 2.39 33.8 Example 8  0.005 3.45 47.9  0.016 3.52 46.9  0.0783.60 46.5 9 *1 — —  0.002 3.65 34.5  0.056 3.80 33.3 10 *1 — —  0.0022.18 33.1  0.059 2.55 33.3 11  0.004 3.54 48.5  0.019 3.47 47.7  0.0823.75 48.3 12 *2 — — *2 — — *2 — — 13 *2 — — *2 — — *2 — — 14 *2 — — *2 —— *2 — — 15 *2 — — *2 — — *2 — — 16 *2 — — *2 — — *2 — — 17 *2 — — *2 —— *2 — — 18 *1 — —  0.001 3.68 35.0  0.032 3.48 34.7 19 *1 — —  0.0022.30 33.8  0.039 2.35 33.3 20  0.005 3.50 47.4  0.018 3.51 45.1  0.0873.56 45.6 *1 Air content exceeds 6% *2 Air content is less than 3% evenif the AE admixture is added in an amount of 0.1%

EXAMPLES 17 to 28 Comparative Examples 21 to 35

The measurement results of the air content entrained in concreteswherein the air-entraining admixture (AE admixture) was added in amountsof 0.002, 0.006 and 0.010% relative to the mass of cement as shown inTables 6-1 and 6-2 are shown in Table 7. The measurement results of thedegree of shrinkage and compressive strength of these concretes are alsoshown in Table 7.

As can be seen from the results in Table 7, the influence of the amountof the added AE admixture on air entrainment is low when the cementadditive composition of the present invention [II] is used

TABLE 6-1 Mix propotion of Concrete AE Sand- Quantity of material perunit Cement Water reducing admix- Slump total volume of concrete (kg/ )additive admixture ture air Water- aggre- Fine Coarse Addition AdditionAddition content, cement gate aggre- aggre- amount amount amounttempera- ratio ratio Water ¹⁾ Cement gate gate Type (%/cement) Type(%/cement) (%/cement) ture (%) (%) E-1 D-1 F-1 G-1 Product 17 C-1 2.0b-1 0.25 0.002 Objective 55 45 165 300 826 1012 of the 18 C-1 2.0 b-10.25 0.006 values 55 45 165 300 826 1012 Invention 19 C-1 2.0 b-1 0.250.010 55 45 165 300 826 1012 20 C-2 2.0 b-1 0.25 0.002 Slump 55 45 165300 826 1012 21 C-2 2.0 b-1 0.25 0.006 18 ± 1 55 45 165 300 826 1012 22C-2 2.0 b-1 0.25 0.010 (cm) 55 45 165 300 826 1012 23 C-3 2.0 b-1 0.250.002 Air 55 45 165 300 826 1012 24 C-3 2.0 b-1 0.25 0.006 content 55 45165 300 826 1012 25 C-3 2.0 b-1 0.25 0.010 4.5 ± 1.5 (%) 55 45 165 300826 1012 26 C-4 2.0 b-1 0.25 0.002 Tempera- 55 45 165 300 826 1012 27C-4 2.0 b-1 0.25 0.006 ture 55 45 165 300 826 1012 28 C-4 2.0 b-1 0.250.010 20° C. 55 45 165 300 826 1012 ¹⁾ Because the cement additive isadded as a part of water, the amount of water + cement additive isshown.

TABLE 6-2 Mix propotion of concrete Slump, Sand- Quantity of materialper unit Water reducing AE air total volume of concrete (kg/ ) Cementadditive admixture admixture content, Water- aggre- Fine Coarse AdditionAddition Addition tempera- cement gate aggre- aggre- amount amountamount ture ratio ratio Water ¹⁾ Cement gate gate Type (%/cement) Type(%/cement) (%/cement) (%) (%) (%) E-1 D-1 F-1 G-1 Compara- 21 R-3 2.0b-1 0.25 0.002 Objective 55 45 165 300 826 1012 tive 22 R-3 2.0 b-1 0.250.006 values 55 45 165 300 826 1012 Example 23 R-3 2.0 b-1 0.25 0.010Slump, 55 45 165 300 826 1012 24 R-4 2.0 b-1 0.25 0.002 18 ± 1 55 45 165300 826 1012 25 R-4 2.0 b-1 0.25 0.006 (cm) 55 45 165 300 826 1012 26R-4 2.0 b-1 0.25 0.010 Air 55 45 165 300 826 1012 27 R-5 2.0 b-1 0.250.002 content, 55 45 165 300 826 1012 28 R-5 2.0 b-1 0.25 0.006 4.5 ±1.5 55 45 165 300 826 1012 29 R-5 2.0 b-1 0.25 0.010 (%) 55 45 165 300826 1012 30 R-6 2.0 b-1 0.25 0.002 Tempera- 55 45 165 300 826 1012 31R-6 2.0 b-1 0.25 0.006 ture, 55 45 165 300 826 1012 32 R-6 2.0 b-1 0.250.010 20° C. 55 45 165 300 826 1012 33 R-7 2.0 b-1 0.25 0.002 55 45 165300 826 1012 34 R-7 2.0 b-1 0.25 0.006 55 45 165 300 826 1012 35 R-7 2.0b-1 0.25 0.010 55 45 165 300 826 1012 ¹⁾ Because the cement additive isadded as a part of water, the amount of water + cement additive isshown.

TABLE 7 Test Results of Concrete Degree of shrinkage Compressive Aircontent (91 days) strength (28 days) (%) (×10⁻⁴) (N/ ) Product of 17 3.7— — the 18 5.2 3.44 34.9 Invention 19 6.8 — — 20 3.5 — — 21 5.0 3.5934.3 22 6.4 — — 23 3.2 — — 24 4.8 3.41 36.7 25 6.3 — — 26 3.5 — — 27 5.23.59 34.0 28 6.6 — — Comparative 21 4.5 — — Example 22 *3   — — 23 *3  — — 24 4.7 — — 25 *3   — — 26 *3   — — 27 *4   — — 28 *4   — — 29 *4   —— 30 *4   — — 31 *2   — — 32 *4   — — 33 5.3 — — 34 *3   — — 35 *3   — —*3 The air content exceeds 8%. *4 The air content is less than 2%.

Industrial Applicability

When the cement additive composition of the present invention [I] isadded to concrete, the discoloration of the surface of concrete can beprevented more easily than by the conventional method. Further, when thecement additive composition of the present invention [II] is added toconcrete, both the influence of the mixed concrete temperature and theinfluence of the amount of the air-entraining admixture (AE admixture)on air entrainment are lower than when the conventionalshrinkage-reducing agent is added, and thus the air content in concretecan be easily regulated.

What is claimed is:
 1. A cement additive composition for preventingdiscoloration of the surface of concrete, comprising a cement additive(a) and a water-reducing admixture (b), the additive (a) comprising amixture of compounds represented by the general formula (1):R₁O(AO)n₁H  (1) wherein R₁ is a C₁₋₆ alkyl group, A is an ethylene groupand/or a propylene group, and n₁ is a number of 1 or more, containingall the compounds satisfying n₁=2 to 6 in a total amount of not lessthan 40% by mass, and having an average n₁ of 1.5 to 10, a molecularweight distribution Mw/Mn of not less than 1.05, a Z average molecularweight Mz of not less than 200 and a ratio of (a):(b) by mass of 5 to99.5:95 to 0.5.
 2. A cement additive composition, comprising (c) acompound or a mixture of two or more compounds represented by thegeneral formula (2): R₂O(AO)n₂H  (2) wherein R₂ is hydrogen or a C₁₋₆alkyl group, A is an ethylene group and/or a propylene group, and n₂ isa number of 1 to 10 on average and (d) a compound or a mixture of two ormore compounds represented by the general formula (3):R₃O(C₃H₆O)n₃H  (3) wherein R₃ is a C₁₋₄ alkyl group, and n₃ is a numberon average more than 10 to 100, the composition having a ratio of(c):(d) by mass of 100:0.01 to
 1. 3. A cement additive compositionaccording to claim 2, wherein (c) comprises a mixture of compoundsrepresented by the general formula (1): R₁O(AO)n₁H  (1) wherein R₁ is aC₁₋₆ alkyl group, A is an ethylene group and/or a propylene group, andn₁ is a number of 1 or more, contains all the compounds satisfying n₁=2to 6 in a total amount of not less than 40% by mass, and having anaverage n₁ of 1.5 to 10, a molecular weight distribution Mw/Mn of notless than 1.05 and a Z average molecular weight Mz of not less than 200.4. A cement additive composition according to claim 2, wherein R₂ is aC₁₋₄ alkyl group, and R₃ is a butyl group.
 5. A cement additivecomposition according to claim 2, further comprising at least onewater-reducing admixture (b) selected from the group consisting oflignin sulfonates, naphthalin sulfonate formalin condensate salts havinga degree of condensation of 5 to 20, melamine sulfonate formalincondensate salts having a degree of condensation of 5 to 20,polycarboxylates aminosulfonate formalin condensate salts having adegree of condensation of 2 to 20 and polycarboxylates containingpolyether group.
 6. A concrete composition comprising a cement, acomposition according to claim 1 contained in an amount of 0.5 to 10%based on the mass of the cement, water and an aggregate.
 7. A concretestructure, obtained by hardening a concrete composition according toclaim
 6. 8. A concrete composition comprising a cement, a cementadditive composition according to claim 2 contained in an amount of 0.5to 10% based on the mass of the cement, water and an aggregate.
 9. Aconcrete structure, obtained by hardening a concrete compositionaccording to claim
 8. 10. A cement additive composition according toclaim 1, wherein R₁ is a methyl group, or a butyl group.
 11. A cementadditive composition according to claim 1, wherein (AO)n₁ in the generalformula (1) is formed by adding ethylene oxide and propylene oxide in ablock form.
 12. A cement additive composition according to claim 1,wherein (b) is at least one compound selected from the group consistingof lignin sulfonates, naphthalin sulfonate formalin condensate saltshaving a degree of condensation of 5 to 20, melamine sulfonate formalincondensate salts having a degree of condensation of 5 to 20,polycarboxylates, aminosulfonate formalin condensate salts having adegree of condensation of 2 to 20 and polycarboxylates containingpolyether group.
 13. A cement additive composition according to claim 1,wherein, when the cement additive composition is added to cement in anamount of 2.25% by mass to obtain a concrete structure, the cementadditive composition allows the surface of the concrete structure tohave a reduction in lightness after 5 years in the range of 2 to
 4. 14.A cement composition comprising a cement and a cement additivecomposition according to claim 1 contained in an amount of 0.5 to 10%based on the mass of cement.
 15. A method of producing a concretestructure, which comprises hardening a concrete composition comprising acement, water and aggregate, wherein the composition containing a cementadditive composition according to claim 1 in an amount of 0.5 to 10%based on the mass of the cement whereby discoloration of the surface ofthe structure is prevented.
 16. A cement additive composition accordingto claim 2, wherein R₂ is a methyl group, or a butyl group.
 17. A cementadditive composition according to claim 2, wherein (AO)n₂ in the generalformula (2) is formed by adding ethylene oxide and propylene oxide in ablock form.
 18. A cement additive composition according to claim 2,wherein, when the cement additive composition and air-entrainingadmixture are added to cement in an amount of 2.25% by mass and in avarying amount from 000.2 to 0.01% respectively to obtain a concretecompositon, the concrete composition has as air content of 2 to 7% byvolume.
 19. A cement composition comprising a cement and a cementadditive composition according to claim 2 contained in an amount of 0.5to 10% based on the mass of the cement.
 20. A concrete compositioncomprising a cement, water, and aggregate and an air-entrainingadmixture of not more than 0.1% by the mass relative to the cement,wherein a cement additive composition according to claim 2 in an amountof 0.5 to 10% based on the mass of the cement is added to the concretecomposition, thereby allowing the influence of the varying amount of theair-entraining admixture on air entrainment to be reduced.
 21. In aconcrete composition comprising a cement, a cement additive, water andan aggregate, the improvement comprising using as the cement additivethe composition according to claim 1 in an amount of 0.5 to 10% based onthe mass of the cement.
 22. In a concrete composition comprising acement, a cement additive, water and an aggregate, the improvementcomprising using as the cement additive the composition according toclaim 2 in an amount of 0.5 to 10% based on the mass of the cement. 23.In a cement composition comprising a cement and a cement additive, theimprovement comprising using as the cement additive the compositionaccording to claim 1 in an amount of 0.5 to 10% based on the mass of thecement.
 24. In a cement composition comprising a cement and a cementadditive, the improvement comprising using as the cement additive thecomposition according to claim 2 in an amount of 0.5 to 10% based on themass of the cement.
 25. A concrete structure, obtained by hardening aconcrete composition comprising a cement, a cement additive, water andan aggregate, the improvement comprising using as the cement additivethe composition according to claim 1 in an amount of 0.5 to 10% based onthe mass of the cement.
 26. In a concrete structure, obtained byhardening a concrete composition comprising a cement, a cement additive,water and an aggregate, the improvement comprising using as the cementadditive the composition according to claim 2 in an amount of 0.5 to 10%based on the mass of the cement.
 27. In a method of producing a concretestructure, which comprises hardening a concrete composition comprising acement, a cement additive, water and an aggregate, the improvementcomprising using as the cement additive the composition according toclaim 1 in an amount of 0.5 to 10% based on the mass of the cementwhereby discoloration of the surface of the structure is prevented. 28.In a concrete composition comprising a cement, water, an aggregate, anair-entraining admixture of not more than 0.1% by mass relative to thecement and another cement additive, the improvement comprising using asthe other cement additive the composition according to claim 2 in anamount of 0.5 to 10% based on the mass of the cement, thereby allowingthe influence of the varying amount of the air-entraining admixture onair entrainment to be reduced.
 29. A cement additive compositionaccording to claim 2, wherein N₃ in the general formula (3) is a numberof 12 to 90 on average.